Play Half-Life with friends! Players fight computer-controlled monsters through the original Half-Life storyline or hundreds of available co-operative scenarios. Also includes a plethora of new weapons, enemies, visuals and gameplay systems. Customization features allow each map to use its own unique weapons and enemies.
I was browsing through the Sven Co-op mod page when I came across this. I clicked on it not knowing what I was getting into. Needless to say, the skeleton spooked me solid. You should have put a screamer warning on this addon because it's 2scary100me. In the end though, 10/10 it's okay.